This invention relates to an electron gun assembly and particularly to an electron gun assembly for use in a multi-beam cathode ray tube in which a plurality of bead straps having angulated grasping members are utilized to secure the bead straps to at least two support rods.
A cathode-ray tube, for example, a television picture tube, usually employs at least one electron gun with an indirectly-heated cathode assembly. Most color television picture tubes employ three such guns. That type of assembly includes a disc-shaped cathode substrate having an electron-emissive coating on the obverse surface thereof and a grid closely spaced from the coating. A coated-wire resistance heater is closely spaced from the other reverse surface of the substrate. The substrate may be supported on a tubular member, which may also contain the heater with two legs of the heater extending therefrom. All of the parts are attached to a pair of common insulating support rods.
Each leg of the heater is indirectly affixed to a common support rod via a heater bead strap. Unlike the grids of the electron gun which are secured between the pair of support rods, each heater bead strap is attached to only one of the support rods. In order to attach the heater bead strap to the support rod, a claw is formed in one end of the bead strap and the claw is embedded into the support rod at an elevated temperature. Frequently, the claw of the heater bead strap is loosely embedded into the support rod so that the heater is free to move during electron gun operation. Such movement, particularly in a multi-beam cathode ray tube having a plurality of cathodes, produces variations between cathodes and adversely affects the electrical characteristics of the electron gun. Additionally, the movement of the heater bead strap may generate particles from the support rod. Such particles are undesirable since they may cause spots on the screen of the tube.